Simplify the following expression: $t = \dfrac{1}{9p} + \dfrac{9}{8p}$
Solution: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $9p$ and $8p$ $\lcm(9p, 8p) = 72p$ $ t = \dfrac{8}{8} \cdot \dfrac{1}{9p} + \dfrac{9}{9} \cdot \dfrac{9}{8p} $ $t = \dfrac{8}{72p} + \dfrac{81}{72p}$ $t = \dfrac{8 +81}{72p}$ $t = \dfrac{89}{72p}$